This invention relates to a motor vehicle seat belt retractor and particularly, to such a retractor having an improved inertia sensitive actuator mechanism.
Most motor vehicles are equipped with seat belt systems which act to restrain the occupants when the vehicle is subjected to high rates of deceleration which may occur, for example, during a motor vehicle collision. Many seat belt retractors are of the so-called emergency locking variety. These retractors employ an inertia sensitive actuator which prevents seat belt webbing from being withdrawn from the retractor when the vehicle is subjected to deceleration forces above a predetermined level, thereby restraining the vehicle occupant. During normal operating circumstances, however, the seat belt webbing may be freely withdrawn from the retractor, enabling freedom of movement by the vehicle occupants.
The inertia sensitive actuator mechanism of a conventional emergency locking retractor includes a spur gear which is attached to one of a pair of toothed sprockets. These toothed sprockets are connected to a rotating belt support shaft. The function of the spur gear is to engage a pawl of the inertia sensitive actuator when the vehicle is subjected to high level deceleration. Once engaged, the inertia sensitive actuator causes engagement between a locking lever and the toothed sprocket thereby preventing continued seat belt webbing withdrawal from the retractor assembly. The spur gear must be accurately positioned with respect to the toothed sprocket. Inaccurate positioning between components can lead to a mechanical failure of the spur gear and/or the remaining components of the inertia sensitive actuator. As a means of accurately positioning the teeth of the spur gear relative to the toothed sprockets, it is current practice to include one or more locating tabs on the spur gear which engage bores or indentations formed by the end surface of the toothed sprocket. It is therefore necessary for an operator to carefully position the parts during assembly.
In accordance with this invention, an improved seat belt retractor of the emergency locking variety is described. The principal improvement in the retractor design resides in providing a spur gear component which is molded directly to one of the toothed sprockets of the retractor. By molding these parts together, precise positioning therebetween can be maintained with a high degree of accuracy. Further, the strength of the spur gear is substantially increased due to its integration with the toothed sprocket. In addition to strengthening the spur gear itself, the connection between the spur gear and toothed sprocket becomes much more secure. Finally, due to the vastly increased strength and dimensional control characteristics inherent in the design according to this invention, a broader range of materials may be employed to form the spur gear component as compared with prior art designs.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.